The present invention relates to a concrete-type composite pipe having large regidity and strength as well as resistance against chemicals, and to a method of producing the same.
Conventional concrete-type pipes exhibit high rigidity and are cheaply produced, but lack resistance against chemicals.
There have further been provided synthetic resin-type pipes exhibiting excellent resistance against chemicals and increased strength. However, such pipes have low rigidity and are expensive to produce.
Furthermore, there have been provided a concrete-type composite pipe in which a corrosion protective layer of a tar-epoxy resin or of a mixture of epoxy resin and aggregate is formed on the inner surface or on the outer surface, or on both the inner and outer surfaces of the steam-cured concrete layer utilizing a conventional cheaply constructed concrete-type pipe that has high rigidity. However, due to difference in the coefficient of thermal expansion and in the coefficient of contraction between the corrosion protective layer and the concrete layer, the corrosion protective layer peels off at the boundary surface relative to the concrete layer. Therefore, the composite pipe could not fully exhibit its function with regard to the strength and resistance against chemicals.
Moreover, the corrosion protective layer is formed by pouring into a vessel a mixture obtained by kneading together the resin and the aggregate, carrying the vessel to pour the mixture onto the inner surface of the concrete layer after it is cured with steam, and spreading the mixture in a centrifugal manner, requiring cumbersome operation for kneading the materials and for carrying the resin. Furthermore, since the mixture lacks flowability, extended periods of time are required before the layer is formed maintaining a uniform thickness.